The game is decent enough, and I certainly like it more than "Plough the skies".
Different levels and specific mission goals are a good thing.
I don't think respawning is done so well, though. If you die in lvl 8 for example, you sometimes respawn at the same interval the V2s are coming: insta-repeat-kill.
Upgrade system is fine and graphics and music fit, I think.
But just like another user said, I cannot pass level 8. I shot every V8 launcher then bombed it to make sure. The rockets disappear but there's no destruction animation for the launcher. I tried 10+ times now, so, yeah I got all 4 of them.
Hope there's a fix! Those medals are tempting. ;)